In the week since Dan Coats announced he was preparing to challenge Democratic Sen. Evan Bayh, Democrats have launched a withering, no-holds-barred assault on the former Republican senator, throwing him off balance and raising questions about whether his prospective candidacy has suffered lasting damage.

The oppo research mill began cranking up within hours of word last week that he was readying a campaign for his former Senate seat in Indiana. First came a Democratic Senatorial Campaign Committee statement referring to him as a “federally registered lobbyist whose client lists include banks, private equity firms and defense contractors.”

Then Coats was blasted for being registered to vote in Virginia, rather than Indiana, and for being soft on Osama bin Laden. The takedown continued as a YouTube video surfaced showing Coats telling North Carolina delegates at the 2008 GOP convention that he was planning to retire to their state.

By Monday, less than a week after he floated the idea of a comeback bid for the seat he held for one full term in the 1990s, Democrats had framed the former senator as a carpetbagger, a Washington lobbyist for PhRMA and big banks and a foreign agent with ties to Venezuelan President Hugo Chavez and Yemeni interests — with almost no noticeable pushback until Coats brought on a campaign spokesman at the beginning of this week.

The ferocious barrage — a coordinated effort unleashed by a small core of senior Democratic strategists in Washington, top Bayh political hands and Indiana Democratic Party officials — has partisans on both sides of the aisle wondering not whether Coats has been bruised by the punches but whether he will be able to pick himself up off the canvas.

“We just hit him with a freight train,” one Democratic official familiar with the anti-Coats effort said Monday. “It’s Politics 101: Frame the guy early.”

Indiana Republican Party Chairman Murray Clark said it was “too early to tell” whether the Democratic attacks had inflicted lasting damage on Coats’s campaign.

“The people of Indiana know Dan Coats. It’s something he’s got to overcome, but with his history I think he can overcome it,” said Clark.

For Senate Democrats, still reeling from the stunning loss in the Massachusetts special Senate election, the pointed attacks suggested a tacit acknowledgment that a lesson had been learned from that experience and that the party is aware it is facing a hostile and unpredictable election cycle, in which no opponent — and no race — can be taken for granted.

Democrats, who say Coats’s entrance into the race caught them by surprise, were nevertheless able to swiftly tap into publicly available information about Coats’s residency history and lobbying career.

“The reason the information is so strong is because it’s readily available. This is easy stuff to find online,” said Dan Parker, the chairman of the Indiana Democratic Party. “I think it’s been very damaging.”

Yet if the Democratic blitzkrieg was geared toward dissuading him from entering the contest, Coats’s campaign says it backfired.

“It just underscores how afraid Democrats are and how credible Dan Coats is as a challenger, and it also draws attraction to the fact that Evan Bayh hasn’t had a competitive race in decades and is very nervous,” said Coats spokesman Kevin Kellems, a former senior aide to Vice President Dick Cheney who came aboard Monday. “Dan Coats isn’t going away.”

Reached Monday and asked for comment on the attacks, Coats said only, “Well, they must think I’m serious.”

So far, Coats’s response has been largely muted. On Friday, after the YouTube video appeared, he wrote a letter to the Fort Wayne Journal Gazette saying that he would very likely be selling his North Carolina home.

James Bopp, an Indiana Republican National Committeeman and Coats ally, said Coats had been focusing his efforts on gathering the 500 petitions he needs in each of the state’s nine congressional districts in order to qualify for the May 4 primary ballot. The deadline for turning in the petitions to state election officials is Feb. 16.

“The concern is not on answering these absolutely fallacious attacks but on qualifying for the ballot,” said Bopp. “He’s properly focused on getting the signatures rather than answering hypocritical attacks.”

A senior GOP operative in Indiana offered a more pessimistic view: “This year is a reaction against D.C. politics, and this is a guy who was right there in the middle of it. That really is a problem in terms of the kinds of contrasts you want to have against Bayh.”

Still, as he lays the groundwork for a campaign, state insiders say Coats faces steep challenges — and not just in weathering the Democratic onslaught. Less than one week after signaling his interest in the race, Coats finds himself racing the clock to meet the petition-gathering deadline.

“This is a tough thing to get done,” said Mike McDaniel, a former state GOP chairman. “To say they have a full-court press on is an understatement.”

“It’s challenging,” said Clark. “It’s an obstacle to everyone.”

Coats has opened an Indianapolis campaign office to help with the process, and Kellems said the campaign began collecting signatures on Friday. Anne Hathaway, a former Republican National Committee chief of staff, is assisting in the petition gathering.

Coats faces an additional hurdle: a crowded GOP primary field where no one has yet blinked at the prospect of his candidacy.

Both former Indiana Rep. John Hostettler and state Sen. Marlin Stutzman, the two best-known candidates, have said they will not stand down.

“With all due respect to Sen. Coats, all the campaigning we’ve done and all the thousands of people that we've spoken to, people are tired of Washington. If there's one group people are more disenfranchised from than Washington politicians, it’s lobbyists,” Stutzman told POLITICO Monday. “Sen. Coats has probably been back to Indiana fewer times than Sen. Bayh has and has those questionable relationships. If you're trying to contrast with Sen. Bayh, why would you go with Sen. Coats?”

Bob Thomas, an Indianapolis auto dealer, told POLITICO Tuesday that he was also interested in entering the GOP contest.

“They’re not just going to get out of his way,” said McDaniel. “Dan’s going to have to get out there and earn it.”